Immediate versus delayed single blastocyst transfer following the first stimulated IVF cycle in the freeze-all strategy: a study protocol for a randomised controlled trial

INTRODUCTION

In recent years, the use of frozen embryo transfers (FET) has rapidly increased following the freeze-all strategy due to the advantages of increased maternal safety, improved pregnancy rates, lower ectopic pregnancy rates and better obstetric and neonatal outcomes. Currently, there is still no good scientific evidence to support when to perform FET following a stimulated in vitro fertilisation (IVF) cycle in the freeze-all strategy.

METHODS/ANALYSIS

This will be a randomised controlled trial. A total of 828 women undergoing their first FET following their first stimulated IVF cycle in the freeze-all strategy will be enrolled and randomised into one of the following groups according to a computer-generated randomisation list: (1) the immediate group, in which FET will be performed in the first menstrual cycle following the stimulated IVF cycle; or (2) the delayed group, in which FET will be performed at least in the second menstrual cycle following the stimulated IVF cycle. The primary outcome will be live birth, which is defined as the delivery of any infants at ≥22 gestational weeks with heartbeat and breath.

ETHICS/DISSEMINATION

Ethical approval was granted by the Ethics Committee of Assisted Reproductive Medicine at the Shanghai JiAi Genetics & IVF Institute (JIAI E2019-15). Written informed consent will be obtained from each woman before any study procedure is performed, according to good clinical practice. The results of this trial will be disseminated in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT04371783.

The optimal timing of frozen-thawed embryo transfer: delayed or not delayed? A systematic review and meta-analysis

Background

The use of frozen embryo transfer (FET) has grown exponentially over the past few years. However, in clinical practice, there are no specific criteria as to whether a delay of at least one menstrual cycle is required for an FET after a failed fresh ET or a freeze-all cycle.

Objective

Through the effects on live birth rate (LBR), clinical pregnancy rate (CPR) and pregnancy loss rate (PLR), to determine whether FET requires a delay of at least one menstrual cycle after fresh ET failure or a freeze-all cycle.

Methods

The search was conducted through PubMed, Web of Science, CNKI, and Wanfang databases for terms related to FET timing as of April 2023. There are no restrictions on the year of publication or follow-up time. Women aged 20 to 46 with any indication for in vitro fertilization and embryo transfer (IVF-ET) treatment are eligible for inclusion. Oocyte donation studies are excluded. Except for the case report, study protocol, and abstract, all original studies are included.

Results

In 4,124 search results, 19 studies were included in the review. The meta-analysis includes studies on the adjusted odds ratio (OR) and 95% confidence interval (CI) of reported live birth rate (LBR), clinical pregnancy rate (CPR), and pregnancy loss rate (PLR), 17 studies were retrospective cohort study, and 2 studies were randomized controlled trial, a total of 6,917 immediate FET cycles and 16,105 delayed FET cycles were involved. In this meta-analysis, the combined OR of LBR was [OR = 1.09, 95% CI (0.93–1.28)], the combined OR of CPR was [OR = 1.05, 95% CI (0.92–1.20)], and the combined OR of PLR was (OR = 0.96, 95% CI 0.75–1.22). There was no statistical significance between the two groups.

Conclusion

Overall, delaying FET by at least one menstrual cycle has no advantage in LBR, CPR, or PLR. So, flexible scheduling of FETs is available to both doctors and patients.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42020161648.

The HERA (Hyper-response Risk Assessment) Delphi consensus for the management of hyper-responders in in vitro fertilization

PURPOSE

To provide agreed-upon guidelines on the management of a hyper-responsive patient undergoing ovarian stimulation (OS) METHODS: A literature search was performed regarding the management of hyper-response to OS for assisted reproductive technology. A scientific committee consisting of 4 experts discussed, amended, and selected the final statements. A priori, it was decided that consensus would be reached when ≥66% of the participants agreed, and ≤3 rounds would be used to obtain this consensus. A total of 28/31 experts responded (selected for global coverage), anonymous to each other.

RESULTS

A total of 26/28 statements reached consensus. The most relevant are summarized here. The target number of oocytes to be collected in a stimulation cycle for IVF in an anticipated hyper-responder is 15-19 (89.3% consensus). For a potential hyper-responder, it is preferable to achieve a hyper-response and freeze all than aim for a fresh transfer (71.4% consensus). GnRH agonists should be avoided for pituitary suppression in anticipated hyper-responders performing IVF (96.4% consensus). The preferred starting dose in the first IVF stimulation cycle of an anticipated hyper-responder of average weight is 150 IU/day (82.1% consensus). ICoasting in order to decrease the risk of OHSS should not be used (89.7% consensus). Metformin should be added before/during ovarian stimulation to anticipated hyper-responders only if the patient has PCOS and is insulin resistant (82.1% consensus). In the case of a hyper-response, a dopaminergic agent should be used only if hCG will be used as a trigger (including dual/double trigger) with or without a fresh transfer (67.9% consensus). After using a GnRH agonist trigger due to a perceived risk of OHSS, luteal phase rescue with hCG and an attempt of a fresh transfer is discouraged regardless of the number of oocytes collected (72.4% consensus). The choice of the FET protocol is not influenced by the fact that the patient is a hyper-responder (82.8% consensus). In the cases of freeze all due to OHSS risk, a FET cycle can be performed in the immediate first menstrual cycle (92.9% consensus).

CONCLUSION

These guidelines for the management of hyper-response can be useful for tailoring patient care and for harmonizing future research.

The time interval between oocyte retrieval and frozen embryo transfer does not impact reproductive outcomes

RESEARCH QUESTION

Does the time interval between oocyte retrieval and frozen embryo transfer (FET) affect pregnancy outcomes after a freeze-all strategy?

DESIGN

Retrospective study including a total of 5995 patients who underwent their first FET following a freeze-all cycle between 1 January 2017 and 31 December 2020. Patients were divided into immediate (the interval between oocyte retrieval and the day of first FET ≤40 days), delayed (>40 days but ≤180 days) and overdue groups (>180 days). Pregnancy and neonatal outcomes were analysed, and multivariable regression analysis was used to study the effect of FET timing on the live birth rate (LBR) in the entire cohort and the different subgroups.

RESULTS

The LBR was significantly lower in the overdue group than in the delayed group (34.9% versus 42.8%, P = 0.002); however, after adjusting for confounding factors, the difference was not statistically significant. The immediate group had a comparable LBR (36.9%) to the other two groups in both the crude and adjusted analyses. Multivariable regression analysis showed no impact of FET timing on LBR in the whole cohort or in the subgroups according to ovarian stimulation protocol, trigger type, insemination method, reason for freezing all, FET protocol or transferred embryo stage.

CONCLUSIONS

The time interval between oocyte retrieval and FET does not impact reproductive outcomes. Unnecessary delays in FET should be avoided to shorten the time to live birth.

Effect of interval between oocyte retrieval and resuscitation embryo transfer on pregnancy outcomes

Objectives

Resuscitation transfer of embryos after elective cryopreservation has been widely applied in in vitro fertilization-embryo transfer (IVF-ET) therapy for human infertility or sterility owing to higher embryo implantation rates. This method separates oocyte retrieval from embryo transfer. The optimal time for frozen embryo transfer (FET) remains unknown. Therefore, this study mainly compares the advantages and disadvantages of delayed FET and immediate FET through retrospective analysis.

Methods

We analyzed real world data of patients who underwent resuscitation transplantation between October 2019 and July 2021 at the Reproductive Center of Chengdu Jinjiang Hospital for Women's and Children's Health. Propensity score matching was applied to control potential confounding factors. A total of 5,549 patients who received at least one FET were analyzed. Patients undergoing transplantation within 60 days of oocyte retrieval were included in the immediate FET group (n = 1,265) and those undergoing transplantation > 60 days after retrieval were included in the delayed FET group (n = 4,284).

Results

Live birth rates between the two groups were comparable (45.25% vs. 45.76%, p = 0.757). Moreover, no difference was observed in the rates of biochemical pregnancy (64.50% vs. 66.80%), clinical pregnancy (55.24% vs. 56.83%), ectopic pregnancy (1.47% vs. 1.39%), early miscarriage (14.41% vs. 16.20%), late miscarriage (2.21% vs. 2.09%), singleton premature delivery (16.67% vs. 18.29%), and neonatal deformity (1.97% vs. 1.80%). After stratifying the patients based on the type of embryo transferred, number of embryos transferred, FET protocol, and good prognosis criteria, live birth rates remained comparable between the two groups (p > 0.05).

Conclusion

Pregnancy outcomes were comparable between the immediate and delayed FET groups.

The association between embryo storage time and treatment success in women undergoing freeze-all embryo transfer

OBJECTIVE

To investigate the relationship between the embryo frozen time and live birth rate (LBR) in women having a freeze-all cycle.

DESIGN

Retrospective cohort study.

SETTING

Academic hospital.

PATIENT(S)

Women who underwent their first vitrified-warmed cycles from January 2013 to December 2019.

INTERVENTION(S)

Embryo storage time.

MAIN OUTCOME MEASURE(S)

The primary outcome was the LBR.

RESULT(S)

A total of 14,928 women were eligible for the analysis. Women with the frozen time of transferred embryos for 2-5 months were associated with a higher LBR compared with other groups. The results were confirmed by an inverted U curve in the restricted cubic splines before as well as after adjustment for covariables, which suggested that an embryo storage time of 3-4 months was associated with the highest LBR. Subgroup analyses demonstrated that the inverted U curve relationship between embryo storage time and LBR was only observed in women with the high response. Sensitivity analyses in women with at least one good-quality embryo for transfer, in women aged <36 years at embryo transfer, or in women with double cleavage embryo transfer showed that the association remained valid. The association was weakened in women with single blastocyst transfer probably because of the small sample size in these women.

CONCLUSION(S)

An inverted U-shaped relationship was found between embryo storage time and treatment success in women with high ovarian response in freeze-all embryo transfer cycles. Prolonged storage time of >6 months was associated with reduced pregnancy rates.

It is not worth postponing frozen embryo transfers after oocyte pickup: A retrospective cohort study based on propensity score matching

This study was to explore whether postponing frozen embryo transfers (FET) after oocyte pickup (OPU) improves clinical and neonatal outcomes. From May 2018 to Dec 2020, a total of 1109 patients underwent their first OPU cycles adopting a non-selective freeze-all policy were included in this retrospective cohort study. In the immediate group (n=219), patients underwent FET in the first menstrual cycle after OPU, and patients in the postponed group (n=890) waited for more than 1 menstrual cycle after OPU to perform FET. A propensity score matching (PSM) model was used to evaluate the clinical outcomes and neonatal outcomes between the two groups. There were 209 patients in the immediate group and 499 patients in the postponed one after PSM. Patients waited for a significantly shorter period for FET in the immediate group (30.74 ± 3.85 days) compared with the postponed group (80.39 ± 26.25 days, P<0.01). The clinical pregnancy rate (CPR) and live birth rate (LBR) in the immediate group were 58.4% and 48.3%, respectively, which were comparable to those of the postponed one (58.1%, 49.7%, P > 0.05). No statistical significance was found in the average birth weight (3088.82 ± 565.35 g vs 3038.64 ± 625.78 g, P > 0.05) and height (49.08 ± 1.87 cm vs 49.30 ± 2.52 cm) of neonates between the two groups. The gender ratio, the incidence of macrosomia and low birth weight did not differ significantly between the two groups. In conclusion, postponing FET does not improve clinical and neonatal outcomes. If patients have no contraindications, FETs should be carried out immediately after OPU.

Immediate versus postponed single blastocyst transfer in modified natural cycle frozen embryo transfer (mNC-FET): a study protocol for a multicentre randomised controlled trial

INTRODUCTION

Today, it is widespread practice to postpone frozen embryo transfer (FET) in a modified natural cycle (mNC) for at least one menstrual cycle after oocyte retrieval and failed fresh embryo transfer or freeze-all. The rationale behind this practice is the concern that suboptimal ovarian, endometrial or endocrinological conditions following ovarian stimulation may have a negative impact on endometrial receptivity and implantation. However, two recent systematic reviews and meta-analyses based on retrospective data did not support this practice. As unnecessary delay in time to transfer and pregnancy should be avoided, the aim of this study is to investigate if immediate single blastocyst transfer in mNC-FET is non-inferior to standard postponed single blastocyst transfer in mNC-FET in terms of live birth rate.

METHODS AND ANALYSIS

Multicentre randomised controlled non-blinded trial including 464 normo-ovulatory women aged 18-40 years undergoing single blastocyst mNC-FET after a failed fresh or freeze-all cycle. Participants are randomised 1:1 to either FET in the first menstrual cycle following the stimulated cycle (immediate FET) or FET in the second or subsequent cycle following the stimulated cycle (postponed FET). The study is designed as a non-inferiority trial and primary analyses will be performed as intention to treat and per protocol.

ETHICS AND DISSEMINATION

Ethical approval has been granted by the Scientific Ethical Committee of the Capital Region of Denmark (J-nr.: H-19086300). Data will be handled according to Danish law on personal data protection in accordance with the general data protection regulation. Participants will complete written consent forms regarding participation in the study and storage of blood samples in a biobank for future research. The study will be monitored by a Good Clinical Practice (GCP)-trained study nurse not otherwise involved in the study. The results of this study will be disseminated by publication in international peer-reviewed scientific journals.

TRIAL REGISTRATION NUMBER

NCT04748874; Pre-results.

Do live birth rate and obstetric outcomes vary between immediate and delayed embryo transfers following freeze-all cycles?

RESEARCH QUESTION

Do live birth rates (LBR), obstetric and perinatal outcomes vary between women who underwent frozen embryo transfer (ET) in the immediately subsequent menstrual cycle, and with those who underwent delayed frozen ET.

DESIGN

Retrospective cohort study (n = 198) consisting of 119 women who underwent immediate transfer within 30 days of oocyte retrieval (OR) and 79 women who underwent delayed transfer which was performed after >30 days following OR. Either flexible antagonist or flexible progestin-primed ovarian stimulation protocols were started after a baseline ultrasonography on the second or third day of menstrual cycle. Only freeze all cycles were included in the study and all transfers were with hormonal endometrial preparation. Main outcome measures were LBR, birth weight, gestational day at birth and pregnancy complications.

RESULTS

Peak estradiol level on trigger day (2746 vs 2081 pg/ml) and number of metaphase-two oocytes (13 vs 10) were significantly higher in the immediate transfer group. Clinical pregnancy rate per ET was similar between the groups (50.4% vs 44.3%). However, miscarriage rate per positive pregnancy was significantly higher (12.3% vs 31.1%) while LBR per ET was significantly lower (42.9% vs 26.6%) in the delayed transfer group. Median gestational age at delivery were 267.5 and 268 days in the immediate and delayed transfer groups. Median birthweight was significantly higher in the delayed transfer group (3520 vs 3195 g). Adjusted analyses also suggest similar LBR with immediate and delayed transfer.

CONCLUSION(S)

Frozen ET in the immediate menstrual cycle and delayed ET, after a freeze all strategy did not show significant difference in terms of LBR after adjustment. Obstetric and perinatal outcomes of frozen ET in the immediate menstrual cycle appear reassuring.

Immediate versus delayed frozen embryo transfer in patients following a stimulated IVF cycle: a randomised controlled trial

STUDY QUESTION

Is there any difference in the ongoing pregnancy rate after immediate versus delayed frozen embryo transfer (FET) following a stimulated IVF cycle?

SUMMARY ANSWER

Immediate FET following a stimulated IVF cycle produced significantly higher ongoing pregnancy and live birth rate than did delayed FET.

WHAT IS KNOWN ALREADY

Embryo cryopreservation is an increasingly important part of IVF, but there is still no good evidence to advise when to perform FET following a stimulated IVF cycle. All published studies are retrospective, and the findings are contradictory.

STUDY DESIGN, SIZE, DURATION

This was a randomised controlled non-inferiority trial of 724 infertile women carried out in two fertility centres in China between 9 August 2017 and 5 December 2018.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Infertile women having their first FET cycle after a stimulated IVF cycle were randomly assigned to either (1) the immediate group in which FET was performed in the first menstrual cycle following the stimulated IVF cycle (n = 362) or (2) the delayed group in which FET was performed in the second or later menstrual cycle following the stimulated IVF cycle (n = 362). All FET cycles were performed in hormone replacement cycles. The randomisation sequence was generated using an online randomisation program with block sizes of four. The primary outcome was the ongoing pregnancy rate, defined as a viable pregnancy beyond 12 weeks of gestation. The non-inferiority margin was -10%. Analysis was performed by both per-protocol and intention-to-treat approaches.

MAIN RESULTS AND THE ROLE OF CHANCE

Women in the immediate group were slightly younger than those in the delayed group (30.0 (27.7-33.5) versus 31.0 (28.5-34.2), respectively, P = 0.006), but the proportion of women ≤35 years was comparable between the two groups (308/362, 85.1% in the immediate group versus 303/362, 83.7% in the delayed group). The ongoing pregnancy rate was 49.6% (171/345) in the immediate group and 41.5% (142/342) in the delayed group (odds ratios 0.72, 95% CI 0.53-0.98, P = 0.034). The live birth rate was 47.2% (163/345) in the immediate group and 37.7% (129/342) in the delayed group (odds ratios 0.68, 95% CI 0.50-0.92, P = 0.012). The miscarriage rate was 13.2% (26 of 197 women) in the immediate group and 24.2% (43 of 178 women) in the delayed group (odds ratios 2.10; 95% CI 1.23-3.58, P = 0.006). The multivariable logistic regression, which adjusted for potential confounding factors including maternal age, number of oocytes retrieved, embryo stage at transfer, number of transferred embryos/blastocysts, reasons for FET, ovarian stimulation protocol and trigger type, demonstrated that the ongoing pregnancy rate was still higher in the immediate group.

LIMITATIONS, REASON FOR CAUTION

Despite randomisation, the two groups still differed slightly in the age of the women at IVF. The study was powered to consider the ongoing pregnancy rate, but the live birth rate may be of greater clinical interest. Conclusions relating to the observed differences between the treatment groups in terms of live birth rate should, therefore, be made with caution.

WIDER IMPLICATIONS OF THE FINDINGS

Immediate FET following a stimulated IVF cycle had a significantly higher ongoing pregnancy and live birth rate than delayed FET. The findings of this study support immediate FET after a stimulated IVF cycle.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was used and no competing interests were declared.

TRIAL REGISTRATION NUMBER

ClinicalTials.gov identifier: NCT03201783.

TRIAL REGISTRATION DATE

28 June 2017.

DATE OF FIRST PATIENT’S ENROLMENT

9 August 2017.

Effects of immediate versus delayed frozen embryo transfer in high responder patients undergoing freeze-all cycles

Background

Frozen embryo transfer (FET) can greatly improve the pregnancy outcomes for high responder patients. However, it is not known whether the timing of FET is a risk factor on pregnancy outcomes in high responder patients undergoing freeze-all cycles.

Methods

A retrospective cohort study to compare the pregnancy outcomes of the immediate and delayed FET groups in high responder patients undergoing freeze-all cycles. The two groups were defined as that FET took place either within the first menstrual cycle following oocyte retrieval or afterwards. Propensity score matching was used to make the potential risk factors of the two groups comparable. Multivariable regression analysis was used to study the effect of the timing of FET on pregnancy outcomes in the entire cohort and propensity score-matched cohort, even in different controlled ovarian hyperstimulation protocol cohorts as subgroup analysis.

Results

We obtained 1130 patients in immediate FET group and 998 patients in delayed FET group, and the average age of the two groups were 30.30 and 30.63. We showed that the immediate FET group were equivalent to delayed FET group in the entire cohort [clinical pregnancy rate (CPR), 61.0% versus 63.4%, adjusted odd ratio (OR), 0.939, 95% confidence interval (CI), 0.781–1.129; spontaneous abortion rate (SAR), 10.1% versus 12.6%, adjusted OR, 0.831, 95% Cl (0.628–1.098); live birth rate (LBR), 49.9% versus 49.2%, adjusted OR, 1.056, 95% Cl (0.883–1.263)]. The same results were obtained by χ² test in the propensity score-matched cohort (CPR, 60.5% versus 63.5%; SAR, 11.6% versus 12.3%; LBR, 48% versus 49.3%) (P > 0.05). Subgroup analysis indicated that pregnancy outcomes of immediate FET were no difference to delayed FET in gonadotropin-releasing hormone agonist (GnRH-a) protocol (P > 0.05). The SAR of the immediate FET group were lower than that of the delayed FET group in GnRH antagonist protocol (adjusted OR, 0.645, 95% CI, 0.430–0.966) (P < 0.05), no differences were observed in CPR and LBR (P > 0.05).

Conclusions

The pregnancy outcomes of immediate FET were no difference to delayed FET in high responder population undergoing freeze-all cycles.

Meta-analysis of the embryo freezing transfer interval

BACKGROUND

The decision of whether frozen embryo transfer (FET) should be performed in the cycle immediately after OPU or at least one cycle later is controversial. FET could improve pregnancy rates in IVF; however, how much time is needed for the endometrium to return to optimal receptivity after ovarian stimulation is not known.

METHODS

Electronic search in MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials to identify studies providing data on the influence of the interval between embryo freezing (or OPU) and FET in FET cycles published between January 1, 2007, and February 1, 2020.

MAIN FINDINGS

Data analyzed indicated that in the immediate FET cycles, there was a trend to an increased biochemical pregnancy rate (RR = 1.08; CI = 1.00-1.18), whereas the clinical pregnancy rate was somewhat higher, but without reaching statistical significance (RR = 1.07; CI = 0.99-1.15). The live birth rate was similar in the two groups (RR = 1.05; CI = 0.95-1.15), as was the implantation rate (RR = 0.98; CI = 0.83-1.16). Stratifying by embryo stage or FET type (freeze-all or FET after failed fresh transfer) showed no differences.

CONCLUSION

Systematically delaying FET does not offer benefits to IVF outcomes. In addition, immediate transfer is associated with a nonsignificant trend to better clinical pregnancy rate and it also avoids the psychological effects of prolonging the stress on prospective parents.

Immediate versus postponed frozen embryo transfer after IVF/ICSI: a systematic review and meta-analysis

BACKGROUND

In Europe, the number of frozen embryo transfer (FET) cycles is steadily increasing, now accounting for more than 190 000 cycles per year. It is standard clinical practice to postpone FET for at least one menstrual cycle following a failed fresh transfer or after a freeze-all cycle. The purpose of this practice is to minimise the possible residual negative effect of ovarian stimulation on the resumption of a normal ovulatory cycle and receptivity of the endometrium. Although elective deferral of FET may unnecessarily delay time to pregnancy, immediate FET may be inefficient in a clinical setting, following an increased risk of irregular ovulatory cycles and the presence of functional cysts, increasing the risk of cycle cancellation.

OBJECTIVE AND RATIONALE

This review explores the impact of timing of FET in the first cycle (immediate FET) versus the second or subsequent cycle (postponed FET) following a failed fresh transfer or a freeze-all cycle on live birth rate (LBR). Secondary endpoints were implantation, pregnancy and clinical pregnancy rates (CPR) as well as miscarriage rate (MR).

SEARCH METHODS

We searched PubMed (MEDLINE) and EMBASE databases for MeSH and Emtree terms, as well as text words related to timing of FET, up to March 2020, in English language. There were no limitations regarding year of publication or duration of follow-up. Inclusion criteria were subfertile women aged 18-46 years with any indication for treatment with IVF/ICSI. Studies on oocyte donation were excluded. All original studies were included, except for case reports, study protocols and abstracts only. Covidence, a Cochrane-tool, was used for sorting and screening of literature. Risk of bias was assessed using the Robins-I tool and the quality of evidence using the Grading of Recommendations, Assessment, Development and Evaluation framework.

OUTCOMES

Out of 4124 search results, 15 studies were included in the review. Studies reporting adjusted odds ratios (aOR) for LBR, CPR and MR were included in meta-analyses. All studies (n = 15) were retrospective cohort studies involving a total of 6,304 immediate FET cycles and 13,851 postponed FET cycles including 8,019 matched controls. Twelve studies of very low to moderate quality reported no difference in LBR with immediate versus postponed FET. Two studies of moderate quality reported a statistically significant increase in LBR with immediate FET and one small study of very low quality reported better LBR with postponed FET. Trends in rates of secondary outcomes followed trends in LBR regarding timing of FET. The meta-analyses showed a significant advantage of immediate FET (n =2,076) compared to postponed FET (n =3,833), with a pooled aOR of 1.20 (95% CI 1.01-1.44) for LBR and a pooled aOR of 1.22 (95% CI 1.07-1.39) for CPR.

WIDER IMPLICATIONS

The results of this review indicate a slightly higher LBR and CPR in immediate versus postponed FET. Thus, the standard clinical practice of postponing FET for at least one menstrual cycle following a failed fresh transfer or a freeze-all cycle may not be best clinical practice. However, as only retrospective cohort studies were assessed, the presence of selection bias is apparent, and the quality of evidence thus seems low. Randomised controlled trials including data on cancellation rates and reasons for cancellation are highly needed to provide high-grade evidence regarding clinical practice and patient counselling.

Time from oocyte retrieval to frozen embryo transfer in the natural cycle does not impact reproductive or neonatal outcomes

OBJECTIVE

To determine if the time from oocyte retrieval to frozen embryo transfer (FET) in the natural cycle affects reproductive or neonatal outcomes.

DESIGN

Retrospective cohort.

SETTING

Not applicable.

PATIENT(S)

Five hundred and seventy-six consecutive freeze-all cycles from January 2011 to December 2018 followed by natural cycle FET of a single blastocyst.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Primary outcome of live birth; secondary outcomes of preterm delivery (24-37 weeks) and small for gestational age (SGA) with a multivariable logistic regression performed with adjustment for age, infertility diagnosis, ovulatory trigger type, and preimplantation genetic testing (PGT).

RESULT(S)

Before adjustment for confounding, we found a statistically significantly different live-birth rate (57.7% vs. 48.6%) for natural cycle FET occurring in the first versus second menstrual cycle, respectively. In a multivariate analysis, performing a natural cycle FET of a single blastocyst in the second compared with the first menstrual cycle did not statistically significantly impact the odds of live-birth rate. After adjustment for age, diagnosis, and ovulatory trigger type, only PGT was associated with statistically significantly increased odds of live birth compared with no PGT. There were no differences in the incidence of SGA (male, 6.6% vs. 2.3%; female, 9.8% vs. 11.1%) or preterm delivery (1.6% vs. 5.6%) between both groups.

CONCLUSION(S)

Performing a natural cycle FET of a single blastocyst in the second compared with the first menstrual cycle after ovarian stimulation did not statistically significantly impact the odds of live birth or neonatal outcomes.

The freeze-all strategy after IVF: which indications?

The freeze-all strategy is gaining popularity worldwide as an alternative to the conventional fresh embryo transfer. It consists of cryopreservation of the entire embryo cohort and the embryo transfer in a subsequent cycle that takes place separately from ovarian stimulation. The freeze-all strategy was initially a 'rescue' strategy for women at high risk of ovarian hyperstimulation syndrome; however, this approach has been extended to other indications as a scheduled strategy to improve implantation rates. This assumes that ovarian stimulation can alter endometrial receptivity in fresh cycles owing to the effect of supraphysiological levels of steroids on endometrial maturation. The procedure, however, has not been associated with increased live birth rates in all infertile couples, and concerns have been raised about the occurrence of several adverse perinatal outcomes. It is, therefore, crucial to identify in which subgroups of patients a freeze-all strategy could be beneficial. The aim of this review is to summarize current scientific research in this field to highlight potential indications for this strategy and to guide clinicians in their daily practice.

Should we still perform fresh embryo transfers in ART?

An increasing number of researchers have alluded to the potential benefit of deferring the transfer of embryos produced during assisted reproductive technologies (ARTs) away from ovarian stimulation, using cryopreservation to enable this. The scientific evidence that may justify this recent trend in the use of the so-called 'freeze-all strategy' includes early, mostly small randomised controlled trials that have demonstrated an increase in live birth rates after elective embryo cryopreservation in certain patient populations, as well as evidence from cohort studies and retrospective analyses. What are the risks and benefits of freeze-all strategies in ART, who are the patients in whom it is likely to be advantageous, and does the current evidence allow us to identify situations when deciding that a fresh embryo transfer would be counter-productive? ART professionals are often faced with challenging clinical decisions regarding the best course of treatment for their patient. The purpose of this opinion paper is to provide a clinical guide for whether to perform a fresh embryo transfer or to opt for freezing all embryos in specific situations.

Delayed versus immediate frozen embryo transfer after oocyte retrieval: a systematic review and meta-analysis

PURPOSE

This systematic review and meta-analysis aimed to compare pregnancy outcomes between immediate frozen embryo transfer (FET) performed within the first menstrual cycle after oocyte retrieval and delayed FET following subsequent cycles.

METHODS

PubMed, EMBASE, and Web of Science were searched for eligible studies through January 2020. The main outcome measures were clinical pregnancy rate (CPR), live birth rate (LBR), and pregnancy loss rate (PLR). The effect size was estimated as risk ratio (RR) with 95% confidence interval (CI) using a random effects model. Inter-study heterogeneity was assessed by the I² statistic.

RESULTS

Twelve retrospective cohort studies involving 18,230 cycles were included. The pooled results revealed no significant differences between delayed and immediate FET in CPR (RR 0.94, 95% CI 0.87-1.03; I² = 67.9%), LBR (RR 0.94, 95% CI 0.85-1.03; I² = 67.5%), and PLR (RR 1.05, 95% CI 0.87-1.26; I² = 42.7%). Subgroup analyses of freeze-all cycles showed a marginal decrease of CPR in delayed FET (RR 0.93, 95% CI 0.86-1.00; I² = 53.6%), but no significant changes were observed regarding LBR (RR 0.93, 95% CI 0.85-1.02; I² = 65.2%) and PLR (RR 1.09, 95% CI 0.84-1.41; I² = 59.1%). No statistical differences were found in effect estimates among other subgroup analyses by ovarian stimulation protocol, trigger agent, endometrial preparation regimen, and embryo stage.

CONCLUSION

Timing of the first FET after oocyte retrieval was not significantly associated with pregnancy outcomes. This finding refutes the current common practice to delay FET after oocyte retrieval and reassures patients who wish to proceed with FET at their earliest convenience. Due to the high heterogeneity and observational nature of included studies, further randomized controlled trials are needed to confirm the results.

Pregnancy and perinatal outcomes in pregnancies resulting from time interval between a freeze-all cycle and a subsequent frozen-thawed single blastocyst transfer

Background

Adverse obstetric outcomes are correlated with altered circulating hormone levels at the time implantation by the trophectoderm. What’ more, embryo freezing process may also have adverse effect on perinatal outcomes. This study aims to evaluate whether increasing interval time between a freeze-all cycle and a subsequent frozen-thawed single blastocyst transfer could have any effect on pregnancy and perinatal outcomes.

Methods

This was a retrospective cohort study included the first single blastocyst transfer in artificially cycles of all patients who underwent a freeze-all cycle between January 1^st, 2016 and September 30^th, 2018. All patients were divided into two groups according to the time interval between oocyte retrieval and the day of first frozen-thawed embryo transferred (FET): Group 1 (immediate FET cycles) and Group 2 (delayed FET cycles).

Results

No significant differences were reported between the two groups regarding the rates of clinical pregnancy, live birth, biochemical pregnancy and pregnancy loss even after adjusting for measured confounding. When accounting for perinatal outcomes, gestational age, birth weight, delivery mode, fetus gender, preterm birth, gestational hypertension, GDM, placenta previa, fetal malformation and low birthweight also did not vary significantly between the two groups. Only the incidence of macrosomia was more frequently in the Group 2 compared with the Group 1 (AOR 3.886, 95%CI 1.153–13.103, P = 0.029) after adjusting with a multiple logistic regression model.

Conclusions

We found delayed FET cycles for blastocyst transfer following freeze-all cycles may not improve the pregnancy outcomes. On the contrary, postponement of FET cycles may increase the risk of macrosomia. Therefore, FET cycles for blastocyst transfer should be done immediately to avoid adverse effects of delayed time on perinatal outcomes.

Delayed frozen embryo transfer failed to improve live birth rate and neonatal outcomes in patients requiring whole embryo freezing

BACKGROUND

Controlled ovarian stimulation (COS) has a negative effect on the endometrial receptivity compared with natural menstrual cycle. Whether it's necessary to postpone the first frozen embryo transfer (FET) following a freeze-all strategy in order to avoid any residual effect on endometrial receptivity consequent to COS was inconclusive.

OBJECTIVE

The purpose of this retrospective study was to explore whether the delayed FET improve the live birth rate and neonatal outcomes stratified by COS protocols after a freeze-all strategy.

METHODS

A total of 4404 patients who underwent the first FET cycle were enrolled in this study between April 2014 to December 2017, and were divided into immediate (within the first menstrual cycle following withdrawal bleeding) or delayed FET (waiting for at least one menstrual cycle and the transferred embryos were cryopreserved for less than 6 months). Furthermore, each group was further divided into two subgroups according to COS protocols, and the pregnancy and neonatal outcomes were analyzed between the immediate and delayed FET following the same COS protocol.

RESULTS

When FET cycles following the same COS protocol, there was no significant difference regarding the rates of live birth, implantation, clinical pregnancy, multiple pregnancy, early miscarriage, premature birth and stillbirth between immediate and delayed FET groups. Similarly, no significant differences were found for the mean gestational age, the mean birth weight, and rates of low birth weight and very low birth weight between the immediate and delayed FET groups. The sex ratio (male/female) and the congenital anomalies rate also did not differ significantly between the two FET groups stratified by COS protocols.

CONCLUSION

Regardless of COS protocols, FET could be performed immediately after a freeze-all strategy for delaying FET failed to improve reproductive and neonatal outcomes.

The Future of Cryopreservation in Assisted Reproductive Technologies

Societal changes and the increasing desire and opportunity to preserve fertility have increased the demand for effective assisted reproductive technologies (ART) and have increased the range of scenarios in which ART is now used. In recent years, the "freeze-all" strategy of cryopreserving all oocytes or good quality embryos produced in an IVF cycle to transfer later-at a time that is more appropriate for reasons of medical need, efficacy, or desirability-has emerged as an accepted and valuable alternative to fresh embryo transfer. Indeed, improvements in cryopreservation techniques (vitrification) and the development of more efficient ovarian stimulation protocols have facilitated a dramatic increase in the practice of elective frozen embryo transfer (eFET). Alongside these advances, debate continues about whether eFET should be a standard treatment option available to the whole IVF population or if it is important to identify patient subgroups who are most likely to benefit from such an approach. Achieving successful outcomes in ART, whether by fresh or frozen embryo transfer, is influenced by a wide range of factors. As well as the efficiency of IVF and embryo transfer protocols and techniques, factors affecting implantation include maternal aging, sperm quality, the vaginal and endometrial microbiome, and peri-implantation levels of serum progesterone. The safety of eFET, both during ART cycles and on longer-term obstetric and neonatal outcomes, is also an important consideration. In this review, we explore the benefits and risks of freeze-all strategies in different scenarios. We review available evidence on the outcomes achieved with elective cryopreservation strategies and practices and how these compare with more traditional IVF cycles with fresh embryo transfers, both in the general IVF population and in subgroups of special interest. In addition, we consider how to optimize and individualize "freeze-all" procedures to achieve successful reproductive outcomes.

Timing of frozen-thawed embryo transfer after controlled ovarian stimulation in a non-elective freeze-all policy

Background

Non-elective freeze-all policy has been increasingly utilized in assisted reproductive treatment, but the optimal timing of frozen-thawed embryo transfer (FET) after controlled ovarian stimulation (COS) remains to be investigated.

Methods

This retrospective cohort study included 2,998 patients who underwent their first FETs after the first COS cycles using the non-elective freeze-all strategy from Jan 2013 to Dec 2016 at a tertiary-care academic medical center. Patients were divided into the "immediate" group in which FET took place within the first menstrual cycle after oocyte retrieval, and the "delayed" group where FET started after one or more menstrual cycles following COS.

Results

The mean interval between oocyte retrieval and FET was 33.3±5.8 days in the immediate group (n=280; 9.3%) and 91.3±19.4 days in the delayed group (n=2,718; 90.7%). Cycles with delayed FET had a significantly lower live birth rate than those with immediate FET before [1,246/2,718 (45.8%) vs. 156/280 (55.7%); P=0.002] and after propensity score matching (PSM) [123/280 (43.9%) vs. 156/280 (55.7%); P=0.005]. When controlling for a number of confounding factors by multivariable logistic regression analysis, the risk remained significant with the adjusted odds ratio (aOR) [95% confidence interval (CI)] of 0.69 (0.53-0.90) and 0.60 (0.42-0.85) before and after matching, respectively.

Conclusions

Performing FET immediately within the first menstrual cycle following COS was associated with a higher chance to achieve live birth compared with delaying FET to subsequent cycles in a non-elective freeze-all policy. However, further randomized controlled trials are still needed to confirm this conclusion.

Frozen embryo transfer at the cleavage stage can be performed within the first menstrual cycle following the freeze-all strategy without adversely affecting the live birth rate: A STROBE-compliant retrospective study

Thus far, all clinical trials evaluating the efficacy of embryo transfer strategies have selectively delayed the first frozen embryo transfer (FET) by at least 1 menstrual cycle. Nevertheless, this approach, which is based solely on clinical experience, may create unnecessary psychological stress on infertile patients who are anxious to conceive as soon as possible. This study aimed to investigate whether the time interval between oocyte retrieval and subsequent FET affects reproductive outcomes.We implemented a large retrospective cohort study in a single assisted reproductive technology (ART) unit at a university-based hospital, including 1540 autologous FET cycles performed in freeze-all cycles. The beginning of the FET was classified as either 'cycle 1' (performing FET within the first menstrual cycle) or 'cycle ≥2' (performing FET after one or more menstrual cycles). Live birth rate (LBR) was the primary outcome of our study.The mean interval for 'cycle 1' and 'cycle ≥2' FETs was 25.72 ± 5.10 days and 75.33 ± 24.85 days, respectively (P < .001). The type of controlled ovarian hyperstimulation (COH) and endometrial preparation protocols differed significantly between groups (P = .008 and P = .004, respectively). However, FET groups were similar in many ways. Univariate analysis showed that there was no significant difference in LBR between the different cycles (33.1% after 'cycle 1' FET vs 34.2% after 'cycle ≥2' FET, P = .68). To evaluate whether LBR remained unchanged after adjustment for potential confounders, we performed multivariate logistic regression. FET timing had no significant impact on LBR in the first FET (odds ratio [OR]: 1.06, 95% confidence interval [CI]: 0.80-1.39).In accordance with the present study, it might not be necessary for clinicians to wait more than 1 menstrual cycle before performing FET. This allows us to reduce otiose deferment in FET, without adversely affecting reproductive outcomes.

Modified natural-cycle cryopreserved embryo transfer: is a washout period needed after a failed fresh cycle?

RESEARCH QUESTION

Are the characteristics of the natural cycle or modified natural cycle (mNC), or live birth rates (LBR), affected by delaying frozen embryo transfer (FET) after a failed fresh IVF cycle?

DESIGN

In a retrospective study, conducted at a university-affiliated tertiary centre, 198 women aged 18-45 years undergoing their first FET cycle after a failed fresh embryo transfer attempt using an mNC were evaluated. Cycles were divided according to the time interval between oocyte retrieval and the start of the FET cycle into the immediate FET group (<22 days) and the delayed FET group (≥22 days). The main outcome measures were ovulation day and LBR.

RESULTS

The mean interval between oocyte retrieval and the start of the FET cycle was 15.6 ± 3.2 days in the immediate FET group and 84.8 ± 73.7 days in the delayed FET group (P < 0.001). Ovulation day was significantly delayed in the immediate FET group (day 17.1 ± 4.4 versus day 15.4 ± 3.7; P = 0.004). There was no difference between the immediate and delayed FET groups in terms of clinical pregnancy rate (CPR) (25.4% and 25.0%, respectively) or LBR (21.2% and 20.0%, respectively).

CONCLUSIONS

Natural-cycle characteristics are similar in immediate and delayed cycles, except for a slight delay in ovulation day. Deferring mNC-FET after a failed fresh IVF cycle does not improve the reproductive outcome. These results should encourage patients and clinicians who want to proceed with FET immediately after failure of fresh IVF.

Ovarian stimulation for preimplantation genetic testing

A narrative review of the management of controlled ovarian stimulation in patients undergoing preimplantation genetic testing is presented. An electronic search was performed to identify research publications that addressed ovarian stimulation and preimplantation genetic testing published until December 2017. Studies were classified in decreasing categories: randomized controlled trials, prospective controlled trials, prospective non-controlled trials, retrospective studies and experimental studies. The aim of controlled ovarian stimulation has shifted from obtaining embryos available for transfer to yielding the maximum embryos available for biopsy to increase the odds of achieving one euploid embryo available for transfer, without the distress of inducing ovarian hyperstimulation syndrome or inadequate endometrium receptivity as vitrification and deferred embryo transfer usually will be planned. The present narrative review summarizes all treatment-related variables as well as stimulation strategies after controlled ovarian stimulation that could help patients undergoing an in vitro fertilization cycle coupled with preimplantation genetic testing, including the number of oocytes needed to achieve one healthy live birth, oral contraceptive pill usage, the role of mild ovarian stimulation or random-start stimulation, the stimulation protocol and type of gonadotropin of choice, the novel progesterone protocols, agonist or dual trigger as a final oocyte maturation trigger, the accumulation of oocytes/embryos and the optimal interval before proceeding with a subsequent controlled ovarian stimulation or the optimal medication to link stimulation cycles. The discussion is being presented according to how questions are posed in clinical practice. The aim of ovarian stimulation has shifted from obtaining embryos available for transfer to yielding the maximum embryos available for biopsy to increase the odds of achieving one euploid embryo available for transfer.

A Comparison of the Miscarriage and Live Birth Rate for Frozen Embryo Transfer According to Two Endometrial Preparations: Natural or Primed with Estrogens

Objective The primary objective is to compare miscarriage rates in frozen-thawed embryo transfer (FET) cycles, according to the endometrial preparation used either artificial through the administration of exogenous estrogen and progesterone or natural without any treatment, during a spontaneous ovulatory cycle. The secondary objective is to compare the live birth rates between the two endometrial preparations.

Study design This is a retrospective study done at KK Women’s and Children’s Hospital Singapore. We included women who underwent FET cycles either with hormone replacement treatment (HRT) or no treatment (natural) for the endometrial preparation, regardless of their cycle number, from 1 January 2011 till 31 December 2015.

Results A total of 2,752 FET cycles were included in our analysis. The natural cycle followed by vaginal progesterone support was used in 1,221 cycles and the HRT cycle with estrogen and vaginal progesterone was used in 1,531 cycles. There is a significantly higher miscarriage rate in the HRT group (38.4%) compared with the natural group (22.3%). The live birth rate is significantly higher in the natural group (22.8%) compared with the HRT group (17.3%). The multivariate analysis further shows that the HRT therapy is independently associated with an increased risk of miscarriage (adjusted odds ratio 2.05; 95% confidence interval 1.45–2.90; [Formula: see text] <0.001) and hence lower odds of live birth (adjusted odds ratio 0.69; 95% confidence interval 0.56–0.84; [Formula: see text] <0.001) after adjusting for the patient’s age at which the embryo was cryopreserved, race, body mass index, main indications for in vitro fertilization, number of embryos transferred and type of embryo transferred.

Conclusion We have shown in this study that the miscarriage rate is higher in the HRT FET group and that this increased miscarriage rate translates into a lower live birth rate in the HRT group. Thus, we conclude that patients with regular menstrual cycles should be offered a natural FET cycle to achieve better outcomes in terms of live birth rate and reducing the miscarriage rate.

The interval between oocyte retrieval and frozen-thawed blastocyst transfer does not affect the live birth rate and obstetrical outcomes

Background

The ‘Freeze all’ strategy, which consists of cryopreservation of all embryos after the ovarian stimulation has undergone extensive development in the past decade. The time required for the endometrium to revert to a prestimulation state after ovarian stimulation and thus the optimal time to perform a deferred embryo transfer after the stimulation has not been determined yet.

Objective

To investigate the impact of the time from oocyte retrieval to frozen-thawed blastocyst transfer (FBT) on live birth rate (LBR), obstetrical and neonatal outcomes, in ‘Freeze-all’ cycle.

Materials and methods

We conducted a large observational cohort study in a tertiary care university hospital including four hundred and seventy-four first autologous FBT performed after ovarian stimulation in ‘freeze all’ cycles. Reproductive outcomes were compared between FBT performed within the first menstrual cycle after the oocyte retrieval (‘cycle 1’ group) or delayed FBT (‘cycle ≥ 2’ group). The main Outcome Measure was the Live birth rate.

Result(s)

A total of 188 FBT were included in the analysis in the ‘cycle 1’ group and 286 in the ‘cycle ≥ 2’ group. No significant differences were found between FBT performed within the first menstrual cycle after oocyte retrieval (the ‘cycle 1’ group) and delayed FBT (the ‘cycle ≥ 2’ group) in terms of the live birth rate [59/188 (31.38%) vs. 85/286 (29.72%); p = 0.696] and the miscarriage rate [20/82 (24.39%) vs. 37/125 (29.60%), respectively; p = 0.413]. The obstetrical and neonatal outcomes were also not significantly different between the two groups.

Conclusion

Our study did not detect statistically significant differences in the LBR for FBT performed within the first menstrual cycle after oocyte retrieval versus FBT following subsequent cycles. Embryo-endometrium interaction after a FBT does not appear to be impaired by potential adverse effects of COS whatever the number of cycle between oocyte retrieval and embryo transfer.

Clinical outcomes of frozen embryo transfer cycles after freeze-all policy to prevent ovarian hyperstimulation syndrome

Objective

To compare the clinical pregnancy rate (CPR) and ongoing pregnancy rate (OPR) in frozen embryo transfers (FETs) following either freeze-all policy to prevent ovarian hyperstimulation syndrome (OHSS; freeze-all group) or excess embryo cryopreservation after fresh embryo transfer (surplus group).

Methods

The freeze-all group comprised 44 FET cycles performed in 25 women between 2010 and 2016. The surplus group comprised 53 FET cycles performed in 47 women during the same period. The cumulative CPR and OPR according to duration of cryopreservation (interval between cryopreservation and FET) was estimated using Kaplan-Meier plots. Cox regression analysis was used for identifying factor to affect to cryopreservation duration in cycles with pregnancy.

Results

In day 2–4 transfer cycles, the crude CPR (40% vs. 18.2%) and OPR (20% vs. 4.5%) were similar between the 2 groups. In day 5 transfer, the crude CPR (33.3% vs. 38.7%) and OPR (33.3% vs. 29%) were also similar between the 2 groups. The cumulative CPR (100% vs. 47.5%) and OPR (100% vs. 33.3%) in day 2–4 transfer as well as the cumulative CPR (46.7% vs. 100%) and OPR (46.7% and 74.8%) in day 5 transfer were also similar between the 2 groups. The median duration of cryopreservation was significantly shorter in the freeze-all group than in the surplus group (19.8 vs. 36.9 weeks, P=0.04). Previous history of delivery was the only factor associated with a shorter cryopreservation duration in cycles with pregnancy (hazard ratio, 0.18; 95% confidence interval, 0.05–0.65; P=0.01).

Conclusion

Freezing embryos to prevent OHSS and transferring the frozen embryos later may guarantee an acceptable reproductive outcome.

Comparison of the effect of immediate versus delayed transfer following a stimulated IVF cycle on the ongoing pregnancy rate of frozen-thawed embryo transfer cycles: a study protocol for a randomised controlled trial

INTRODUCTION

Frozen-thawed embryo transfer (FET) has become an increasingly important part of in-vitro fertilisation (IVF) treatment. Currently, there is still no good scientific evidence to support when to perform FET following a stimulated IVF cycle. Since all published studies are retrospective and the findings are contradictory, a randomised controlled study is needed to provide Level 1 evidence to guide the clinical practice.

METHODS/ANALYSIS

This is a randomised controlled trial. A total of 724 women undergoing the first FET following ovarian stimulation in IVF will be enrolled and randomised according to a computer-generated randomisation list to either (1) the immediate group in which FET will be performed in the first cycle following the stimulated IVF cycle or (2) the delayed group in which FET will be performed at least in the second cycle following the stimulated IVF cycle. The primary outcome is the ongoing pregnancy defined as a viable pregnancy beyond 12 weeks' gestation.

ETHICS AND DISSEMINATION

Ethical approval has been granted by the Ethics Committee of Assisted Reproductive Medicine in Shanghai JiAi Genetics & IVF Institute (JIAI E2017-12) and from the Institutional Review Board of the University of Hong Kong Hospital Authority Hong Kong West Cluster (UW 17-371). A written informed consent will be obtained from each woman before any study procedure is performed, according to good clinical practice. The results of this trial will be disseminated in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT03201783;Pre-results.

Thawed embryo transfer and ectopic pregnancy: a meta-analysis

PURPOSE

To examine whether thawed embryo transfers can reduce the rate of EP.

METHODS

The PubMed, EMBASE, Cochrane Library databases and two randomized controlled trials registration centers were thoroughly searched until March 2017. The clinical outcomes of IVF/ICSI cycles were compared between thawed and fresh embryo transfer.

RESULTS

Twenty-one articles were included in this meta-analysis. There were 801,464 pregnancies totally (thawed-ET: n = 158,967, fresh-ET: n = 642,497). The ectopic pregnancy rate was significantly lower in the group of thawed-ET than that in the group of fresh-ET (OR 0.69, 95% CI 0.57-0.82; I² = 83%). We subdivided the data into subgroups for D3 embryo transfer and D5 embryo transfer. We also found that the ectopic pregnancy rate was significantly lower with thawed-ET on D3 than that with fresh-ET (OR 0.67, 95% CI 0.53-0.85; I² = 0%). The risk of ectopic pregnancy was significantly decreased with thawed-ET on D5 than that with fresh-ET (OR 0.57, 95% CI 0.50-0.64; I² = 45%).

CONCLUSION

Our results indicate that in contrast to fresh embryo transfers, thawed D3 or D5 embryo transfers can reduce the rate of EP.

Frozen blastocyst transfer outcomes in immediate versus delayed subsequent cycles following GnRH agonist or hCG triggers

PURPOSE

The aim of this study is to analyze clinical pregnancy rates (CPR) and ongoing pregnancy rates (OPR) for frozen embryo transfers (FET) performed with blastocysts in the cycle immediately after GnRH agonist (GnRHa) versus human chorionic gonadotropin (hCG) triggers, with outcomes of delayed FET for comparison.

METHODS

Retrospective cohort study at a university-affiliated in vitro fertilization (IVF) clinic, including patients undergoing IVF between 2013-16 with a blastocyst FET performed within two menstrual cycles of a previous stimulation cycle and vaginal oocyte retrieval (VOR). FETs included programmed and natural endometrial preparation. Outcome measures were clinical and ongoing pregnancy rates.

RESULTS

CPR and OPR for 344 FET cycles were similar when comparing immediate and delayed transfer overall (crude CPR 67.5 versus 76.5%, p = 0.11; OPR 57.5 versus 66.7%, p = 0.13), and after stratifying by cycles following hCG trigger (OPR 62.5 versus 66.3%, p = 0.61) and GnRHa trigger (OPR 55.6 versus 64.5%, p = 0.17). When considering a number of predictors for OPR, an adjusted odds ratio (OR) of 1.74 [95% CI 1.00-3.03] approached significance in favor of delayed FET.

CONCLUSIONS

Regardless of trigger modality, patients can be reassured that pregnancy rates with FET are high in immediate and delayed cycles. However, our study suggests a potential benefit in delaying a cycle before proceeding with FET.

Should we continue to measure endometrial thickness in modern-day medicine? The effect on live birth rates and birth weight

The evaluation of endometrial thickness (EMT) is still part of standard cycle monitoring during IVF, despite the lack of robust evidence of any value of this measurement to predict little revalidation in contemporary medical practice; other tools, however, such as endocrine profile monitoring, have become increasingly popular. The aim of this study was to reassess whether EMT affects the outcome of a fresh embryo transfer in modern-day medicine, using a retrospective, single-centre cohort of 3350 IVF cycles (2827 women) carried out between 2010 and 2014. In the multivariate regression analysis, EMT was non-linearly associated with live birth, with live birth rates being the lowest with an EMT less than 7.0 mm (21.6%; P < 0.001) and then between 7.0 mm and 9.0 mm (30.2%; P = 0.008). An EMT less than 7.0 mm was also associated with a decrease in neonatal birthweight z-scores (-0.40; 95% CI -0.69 to -0.12). In conclusion, these results reaffirm the use of EMT as a potential prognostic tool for live birth rates and neonatal birthweight in contemporary IVF, namely when considered together with other ovarian stimulation monitoring methods, such as the late-follicular endocrine profile.

Frozen embryo transfer can be performed in the cycle immediately following the freeze-all cycle

PURPOSE

In this study, we investigated whether the time interval between oocyte retrieval and frozen embryo transfer (FET) affected the live birth (LB) rates of human segmented-IVF cycles.

METHOD

A total of 1338 ICSI freeze-all cycles were performed between February 2015 and January 2016, with 1121 FET cycles being retrospectively analyzed. All vitrified-warmed blastocyst transfers were performed in artificial FET cycles, using gonadotropin-releasing hormone (GnRH) agonist downregulation and oral estrogen endometrial preparation. The primary outcome measure was LB. Cycles were investigated in oocyte retrieval-to-FET interval groups of 32-46, 47-61, 62-76, 77-91, and ≥ 92 days, with the 47-61-day group used as the reference group.

RESULTS

There were no significant differences in LB rates between the groups in the overall analysis, as well as, in sub-analyses investigating LB in terms of single blastocyst transfer (SBT), trigger type (GnRH agonist, triggers including hCG), oocyte number (≤ 5 and ≥ 15), and maternal age (> 35 years).

CONCLUSION

The present study showed that it is feasible to perform transfers 36 days after oocyte retrieval and that delaying FET in freeze-all beyond the cycle immediately following oocyte retrieval does not increase LB rates.

Ectopic pregnancy following in vitro fertilization: meta-analysis and single-center experience during 6 years

BACKGROUND

Ectopic pregnancy (EP) has been reported to occur in 1.4-5.4% of all clinical pregnancies resulting from in vitro fertilization (IVF) and embryo transfer (ET). Data on factors associated with abnormal embryo implantation following assisted conception are limited.

MATERIALS AND METHODS

A systematic review and meta-analysis was performed to determine whether there is an association between the day (cleavage-stage, D3, versus blastocyst, D5) or the type (fresh versus frozen/thawed) of ET and EP rate. Risk factors for EP were evaluated in a retrospective study of 1194 women, who achieved pregnancy at our IVF unit between 2010 and 2016.

RESULTS

Sixteen papers were considered for the meta-analysis. EP rate did not differ between D3 and D5 fresh ET groups (RR = 0.99, 95%CI: 0.76-1.30) and was higher after fresh versus frozen ET (RR = 1.56, 95%CI: 1.25-1.95). At our clinic, 21 (1.76%) pregnancies were documented as ectopic. The risk of EP was associated with tubal pathology (OR = 3.37, 95%CI: 1.39-8.2), previous appendectomy and past chlamydial infection.

CONCLUSIONS

Present meta-analysis suggests that EP rate is similar following fresh blastocyst and cleavage ETs, but is significantly reduced after frozen compared with fresh ET. Our own findings demonstrate that tubal pathology has the major impact on EP occurrence following assisted conception.